Frequency multiplier apparatus



April 24, 1956 E. P. FELCH ETAL FREQUENCY MUL-TIPLIER APPARATUS Filed April 23, 1953 @SSN E G. MERR/LL wvw ATTORNEY FREQUENCY MULTIPLIERAREAR'IUS t EdwinfPf FelclifandlLFrancis G. Merrill; Chatham, N; Ja', assignors 'toi Bell -TelephoneiLalmratores, lvlncorporated, New York, N.- Y., a corporation: offNWfYork Application April 23, 1'953'QScrilNo. 350,702y 5.'.Claimsgf (615250-246) This invention relates to frequency multiplier:` apparatus, andA particularly. toU frequency multiplierf apparatusfof the phase shifttype which may beutilized tozniultiply-y an applied input or fundamental lsine;wave of frequency F to a substantially sine wave. output harmonic.- multiple States Patent O thereof 'of frequency nF, where.n.may-,be any-harmonic value of the applied vinputfr'equency F accordingito the number. of phase shiftedwaves selected. from.v each cycle or. wavelength of 'the.appliedfundamentals input wave'.

One of theobjects of 'this inventionis .toplrovide a phase shift type frequency multiplier.

Another object offthisl inventionfisy tofprovideisuclra frequency multiplier havingreduced losseseand. other ad7 vantages,r particularlyl where-factors; of! increased freT ,quencies and increased'fequency-.- multiplication. may be involved."

Another object .ofi this inventionsisto providea frequency multiplier which .willlhave a.v sulistantially linear input-output amplitude. level relationshipv over.. a; reason.- able range of input amplitudlvel..

Another object of"thisivention.isztoprovidecaefre,

quency multiplier Whichwilllgenerate odd-harmonic.mulf tiples; of 'the input frequency, ,particularly in .combination with.y the previous objectives.i

Another object of this invention i's.to provide altref quency multiplier in which theparticular, desiedhar.- monic frequency output isaccentuated"l Wihrespect to unwanted harmonic outputs.

Conventional frequency multipliers. for.. multiplication ratiosi of; three. or greater usually employ distorting5de? vicessuch' as overloaded'oroverbiased'electron tubes.or varistorsto produce a'dis'tortedwaveform containingthe desiredharmonic which maybe selctedbyfmeans. of; an outputtuned circuit or.filter. Since, in. such distortion type'multipliers, Vthefndamental.l and. adjacent frequency prodcts;may be present in th'e outputcicuitl. ata level equalto' or above that of the d'esired'liarmonic-` produc-t, tli`eout'put'v filter usedltherewit'li usually must.b'e. made. to raii'orda. relativelyN h'igl order. of discrimination. This maydnvolvc the use of, sucli high eiective-Q1s or such large multiplelter sections as to result in a relatively steep phase versus frequency characteristic, a .characteristie which may not be compatible with optimumph'ase stability,v particularly in casesl wherel the. llter is .operated outof a saturated electron tube. The phasev shift type of frequency, multiplier apparatus providedin.` accordance with this invention may avoidlthis diflcult'y bysynthesib ing` a wave which contains predominantly,k the desired har.-

monic and which consequently may; requireonly. a. minimum of "filtering, to Aeliminate unwanted products.

In'Y accordance with. this invention,` an.; input wave of frequency F; ,to be multiplied to the desired-harmonic frequency nF', may beapplied toone end of a pliaseshift type transmission line, such as a lumped constant iterative network type lineor a .distributedconstant line, Iand may be synthesized by addingthepeaks ofiwaves. therein suc.- cessively shifted in phase with respect to the Vphase of the 2f. originalapplied. inputfrequency wave. or. signal.v In.. this arrangement, Ythe unitary phaseshifttype transmssionline may, beutilied tofprovide. the/separate phase shifted waves or signals; and diodes, v varistors or. other. suitable unilateral conductive devices connected to appropriate tap p ointSJon the phase shift transmission .line may. be utiliied to'tap oiffandlselect atvany instant the phase shiftedwave orlsignalcfgreatest' amplitude and pass .it to a common outpnt'cir'cuit;

Accordingly',l asa feature of this invention, an iterative phaseshift'typeof transmission line suchias'an iterative phiseshift'l lumpedl constant line comprising a tandem seriesofphase shifting network sections or'an' iterative phasev shift vdistributed constant line`comprising a" tandem seriesL of phase shifting line se'ctionsunayV he' utiliz'edi'to obtain therein thev desiredr number.4 of phase' shiftl'ed'siggy nals which may be tapped" off therefrom; rectified" and combined intheecommon` output loadcircuit.v

Also, as `an'adclitionalffeature of this"invention', one or morek additional phase shift sections-may be provided atthe eudiofthefphase shift ytransmission'line-beyondithe last rectifierI tap pointthereon, and futilizedl as impedance termination-means therefor' and* also as means for acljustingr'the uniformity of fth'e; output wave:

Also, f as additionahfeatures of this invention; resistors may beprovided'fbetween anyor all of fthe' respective june# tion tap'- points on f the vph'ase` sh'ift transmission line and their: associated."y respective` rectifiers to con'ipensatefA for diiferencesf. inl level. of? current 1 su'pfplietl'. to: the lcommon output icircuit; and' the: outputload: circuit may be f made ofjrelatively hig'hlimpednce: compared. withrathe' imperiL ancer off. the phase;y shifti transmission lineinf orders' te equa-lifzefxthersigna'ls;.miniinizcf distortion 'ofitheliiiercunL rents; and for otherrpnrposesc;

' The: present invention provides f a frequency-'multiplier which is: relativelycsimple: tot: construct?. and? operate, and which; gives: 1 an foutpnt frequencyv thatrislfan: odd.' or .leven multiple f nB-iofil its; applied-f. input.' or." fundamental: fequency F and that is substantially freei-fromithet'lattcr frequency/F". v Y

Fortawclearerunderstanning:tof; thevnaturerofftliisuiiwenf tion and theadditional advantag'ea.featuresv'andsobjects thereof;` refer-ence.' isf-made." to* the followingr: description taiceminlconnectionrwithztlei accompanying drawingsyin whieh-lilce refereneechara-cters represent like or similar partssandimvhich: 1

Figc; 1| is:r an schematic circuit diagrarm illustrating: a phasefshift typerfrequencyl multiplier. apparatusf-inraccordi ance@ Wi'th thiss'invention; :wherein .f thefapplied sinef wave inputrfreiquency lizmay;` be: mnltipliedfto: an outputzzs'ubzstantially;` sine.: wave: harmonicr frequency;` nF" which. in therexample-illustratcdrinffFigv 1, involvesfa harmonic value of nF: 5F;

Eig; .2: isiazzgraphaillustrating:an fexample'rof input and outputwave.- f'orm-sw for: thee frequency; multiplier' circuit shownlfin Fig.5..l curvefAw of-tFi'g. '2 representing anf'in'p'ut siner wavel oliiy frequency F as?. applicdaat-,point f A ftof the input-,of the frequencyymul-tiplierfin'iFig: 1; andcurvesB of; Fi 2- .represeating;` an` =output1sine wave of 2 harmonic Referring to the drawing, Fig. 1 is a circuit diagram illustrating a phase shift type frequency multiplier apparatus, showing particularly a quintupler form thereof adapted to frequency multiply an applied input or fundamental sine wave frequency F as illustrated by the curve A in Fig. 2, to an output sine wave harmonic multiple frequency nF=5F as illustrated by the curve B in Fig. 2.

As particularly shown in Fig. 1, the circuit may generally comprise an input circuit source of frequency F including an amplifier V1 and its associated tuned input and output circuit components which may be of any suitable form, a phase shift type frequency multiplier FM having its input A connected to the tuned output circuit of the input amplifier V1 and having its tuned output B connected to the input of an output load circuit amplifier V2 which may be of any suitable form. The frequency multiplier part FM of the apparatus illustrated in Fig. 1 has its input between the input terminal A thereof and ground G, and its output terminals between the output terminal B thereof and ground G.

As shown in Fig. l, the input circuit for the frequency multiplier FM may comprise an input source of sine waves of frequency F applied at input terminals 10, 11 and connected through a coupling condenser C12 to the input of a suitable pentode type amplifier tube V1. The tube V1 may be provided with a suitable control grid input circuit resonant network which may include therein a tuning inductor L and capacitors C10, C11 tuned to the input frequency F, and voltage peak limiters comprising varistors or germanium crystal diodes D10, D11 connected to form a clipper circuit which may be utilized to insure constant maximum voltage. As shown in Fig. l, the plate circuit for the amplifier tube V1 may comprise a resonant network, including a tuning inductor L14 and capacitors C14, C15, which may be tuned to the input frequency F and utilized to transform the impedance in the plate circuit of the tube V1 for use at the input terminal A of the unitary phase shift transmission line S1 to S5 of the frequency multiplier FM. The plate and screen supply voltages for the amplier tubes 'V1 and V2 maybe obtained from a suitable +B power supply source 10.

As particularly shown in Fig. l, the phase shift trans'r mission line of the frequency multiplier FM may comprise a unitary or undivided lumped constant type line consisting of a plurality of three-mesh phase-shifting iterative network sections S1 to S5 comprising series inductors L1 to L5 and shunt capacitors C1 to C6. In this arrangement, each of the phase shift sections S1 to S5 may contribute a successive phase shift of one-fifth cycle or 72 degrees of the applied input frequency waves and thereby provide at the successive ve junction tap-off points 1 to 5 thereon tive waves of the input frequency F each having a relative successive phase shift of one fifth (one nth) of one cycle or wavelength of the applied input frequency wave.

Accordingly, in the particular case of the quintupler example shown in Fig. 1, live individual voltages each differing in phase by 72 degrees or one fifth of one cycle of the input frequency wave F applied at A, may be obtained from the five respective junction tap points 1 to 5 located on or between the respective phase-shifting network sections S1 to S5, and such voltages may be adjusted to equal or uniform magnitude by means of the associated respective series resistors R1 to R4 to compensate for line losses and other effects and then individually applied to their associated five respective half wave crystal diodes or other suitable rectitiers D1 to D5, the resistors R1 to R4 being utilized to adjust the relative amplitude levels of the respective voltages individually supplied to the five respective rectiiers D1 to D5.

Each of the five rectifier diodes or varistors D1 to D5 conducts as the voltage applied thereto becomes greater than that of the others and since there are, in the quintupler example shown in Fig. 1, live such rectifiers D1 to D5, there will be tive successive pulses supplied at the common output circuit line C of the rectifiers D1 to D5 for each cycle or wavelength A of the input wave applied at input A to the phase shift transmission line S1 to S5. These live pulse type waves, which may be made nearly equal and sinusoidal, represent the outputs of the five half-wave polyphase rectiers D1 to DS and may be combined in the common output or load circuit at C which may be connected to the output terminal B of the frequency multiplier FM, through a series resistor R8 and a tuned circuit comprising a parallel-connected tuning inductor L8 and capacitor C8 having a relatively high Q for wave shaping purposes. The resistor R8 may be utilized to prevent the phase shift transmission line S1 to S5 from shunting the output circuit resonant network L8, C8, and may be made of relatively high resistance values, roughly the same as the tuned impedance of network L8, C8, such as of an impedance value of some ten times higher than the impedance of the phase shift transmission line S1 to S5, in order to prevent loading the latter and destroying its transmission line characteristics.

As shown in Fig. l, the output terminal B of the frequency multiplier FM may be applied to the input or control grid circuit of the output amplifier V2 which may be a pentode type vacuum tube provided with a tuned plate circuit consisting of a parallel-connected tuning inductor L20 and capacitor C20, and utilized to step t down the impedance into the final output circuit load terminals .20, 21. The tuned input and output circuits L8, C8 and L20, C20 for the amplifier tube V2, being tuned to the desired output harmonic frequency nF, may also provide additional filtering of the pulse type waves applied thereto from the outputs of the rectifiers D1 to D5.

As shown in Fig. 1, the phase shift transmission line S1 to S5 may be provided with end termination means in the form of one or more additional or end network sections, such as the termination or end phase shift network section S5 shown in Fig. 1 as comprising a series inductor L5 and a shunt capacitor C6 and also shunt resistor R7, all dis posed beyond the last or end junction tap point 5 connected to the last rectifier D5 and which, in accordance with a feature of this invention, may be utilized to adjust the uniformity of the output wave.

Adjustments in the multiplier circuit of Fig. 1 may be made with the aid of an oscilloscope and a voltmeter. With the voltmeter connected to the input of the frequency multiplier line between the terminal A and ground G, and with an input signal F sufiiciently low that the limiter D10, D11 is inoperative, the input frequency network L10, C10, C11 and L14, C14, C15 may be tuned for maximum voltage at A into the frequency multiplier transmission line S1 to S5. Curve A of Fig. 2 illustrates the input frequency F voltage waveform with the limiter D10, D11 working. Then with the oscilloscope connected to the common output point C of the rectifiers D1 to D5, adjust the inductors and capacitors L1 to L5 and C1 to C6 of the phast shift transmission line S1 to S5 for pulses of equal amplitude and phase, using the resistors R1 to R4 to compensate for differences in level. This is illustrated in Fig. 2A. After these adjustments are made as well as possible, the voltmeter may be connected to the output terminals 20, 21 and the output circuit networks L8, C8 and L20, C20 for the tube V2 may be tuned for maximum voltage. Curve B of Fig. 2 illustrates the output frequency nF voltage wave form as compared with the input frequency F voltage wave form of curve A, the frequency components in curve B being fifth harmonics of the input frequency F shown in curve A.

As an illustrative example in a particular case for the quintupler form of frequency multiplier as illustrated in Fig. 1 and wherein the input frequency F is assumed to be a sine wave frequency F=1 megacycle per second as illustrated by curve A of Fig. 2 and wherein the harmonic affamata? output firequencyv nF'isl substantiatllyJ a -sinewave 'fequency nF=5 megacycles perJ second as illustrated' b'ycurverB in-F'gry 2, the circui-tof Fig; lmayltavecthe'following componentfvaluesvapproxirnately:` The input-and output circuitiamplitier tubes V1- and V2`may'be conventional 401A' type pentodes, or: otherv suitableamplifiers: The rectifiersDly to D5, Dl and' D11 may ybeanysuitt'tble rectifier means as varistors or crystal1 diodes: The' resistors for the present example may haveresistance-'values ofthe-following approximate values'- as expressed in ohms: R-1=4'7(),V R21-360, R3=2402r R4"=l20y R7=5l0, R8l=4700, R10=2`l60,^ E111-2160,' R12i=l00000"and REL-:1500: The capacitors for the present'example'may have capacitanceA values ofL the following approximate valesl as exp-ressed inv inicro-microfarads.w C1` to C5 each=480 to 520, C6=23O to 270, C8=68, C10 and C11 each==100.0,zC12=7 to:45;'C13"=100;000}.C14=560, C15=330, C16=l000,l C20=50, C21=18; yC22-:250,000 and C23=680. The inductors for the present example mayhave -the following approximate Aindt'lctancevalues'as expressedinf microhenries: L1i to' L5" each=`72`V to^'80, L8`=l3 toI 15, L10=l, L14=80 to 100, L20"=l3=`l5. TheV one'megacycleper second fundamental input frequency F inthe example given-above,- may beat`a'75 ohm input at 0.05 -volt,` and thefve-megacycle per-second harmonic'output frequency'nF may'be'into 'a-75"'ohm outputiat 0;'5volt-at-the-outputl terminals 20, 21;

While the particular frequency multiplier circuit of i Fig. 1 'is by way of illustrative example shown as a quin tupler, as for multiplying a one megacycle per second input frequency F to a tive megacycles per second output frequency nF=5F, it will be understood that other values of input frequencies F and other values of frequency multiplication of ratios n may be utilized by the useIof suitable circuit values therein.v

Also, while the phase shift transmission line S1 to S5 of Fig. l is shown therein as comprising network sections of series inductors L1 to L5 and shunt capacitors C1 to C6, it Will be understood that other forms of lumped constant phase shift transmission lines may be utilized comprising phase shifting network sections each of at least two of inductance, capacitance and resistance elements, such as network sections of capacitance and resistance elements for example for use at the lower frequencies; and that other forms of phase shift transmission lines comprising phase shifting sections of a distributed constant type transmission line may be utilized at the higher frequencies, as illustrated in Fig. 3 for example.

Fig. 3 is a circuit diagram illustrating a modification of the invention utilizing a phase shift transmission line comprising a distributed constant type line L having phase shifting sections S1 to S5, instead of a phase shift transmission line of the lumped constant type shown in Fig. l.

As illustrated in Fig. 3, the line L may be of the coaxial conductor type having junction tap points 1 to 5 at appropriate points spaced along the electrical length thereof to provide the desired number of phase shift sections therein corresponding to the phase shifted waves to be applied to the respective rectiiiers D1 to D5 the outputs of which are combined in the common output line C, as in Fig. l. As shown in Fig. 3, the electrical length of line L is at least one wave length 7k corresponding to the fundamental input frequencyV F applied thereto from the input terminal A, the phase shifted signals being tapped off from the respective junction tap points 1 to 5 thereof to provide at output B the desired harmonic output frequency nF=5F in the particular quintupler example illustrated in Fig. 3, and the operation being similar to that described in connection with Fig. 1.

While in Figs. l and 3 the phase shift transmission line is shown provided with junction tap pointsy 2 to 5 between each of the individual phase shift sections S1 to S5, it will be understood that the junction tap points may be placed between alternate or others of the phase shift sections made of suitable number and phase shift 6 therebetween to provide the desired: harmoniel of-itlie fundamental' input waveappliedVv thereto.4

Although this invention has?Y been f described andy illus'- tratedfirrrelationv to-spec-itearrangements;` it visito .b'eunderstoodf that'it is capable"offapplication' in other organizations-andis thereforefnotfto belimited to the particular embodimentL disclosed:

Whatf'fis claimed: is:

1S Fequency multiplier apparatuscomprising"arsource ofinputfequency; sine I waves,- and'- means forfr'equeney multiplying'said source'- input frequency' sinewaves'to Harmonic: output frequencyl waves' thereof of sine wave form` comprising' a phaseV shift transmission line connectedladjacent one end `-thereof ytosaid sourceand comprisingaiplurality of iterativetandem=disposed phase shift sections each having a reactance value-suicientfor'com triuting successivephase) shifts in saidiiiputV fi'equency waves therein iti-accordancev with tlieeorderofisaidharmonicofsaid output frequency wavesv and-correspondiirg iirphaseI sliiftto anfinegralj'ffr'action of 'one-cycle ofisaid inputfrequency waves, a pluralityV offjunetion tapk connection pointsvfor; atleastsomelof said: phase shiftsections forV individually tappingy off said successivepltase shiftedwavesfromsaid phasesliift transmission line, a plurality r of"rectiii'erv means individually connected to said respective junction tap points forrrectifying said'y successivephase shifted' wavesl received from said phaseshift transmission line, means including a common output load :circuit connected to and combining the outputs of said rectiiied waves received from said respective rectifier means for obtaining in said output circuit said desired harmonic output frequency waves, termination means for said phase shift transmission line adjacent the other end thereof comprising at least one of said phase shift sections disposed beyond the last one of said junction tap points, and resistance means individually connected in series between at least some of said junction tap points and their said respective rectifier means for controlling the relative am plitude levels of said phase shifted waves therein, said output load circuit including therein a series resistance means connected with said plurality of rectier means and having a substantially higher impedance value than the over-all impedance value of said phase shift transmission line, said output load circuit including a resonant circuit connected with said last mentioned series resistance means and tuned substantially to said desired harmonic output frequency.

2. Frequency multiplier apparatus comprising a source of input frequency sine waves including electronic ampliiier means having resonant input and output circuits tuned substantially to said input frequency, and means for frequency multiplying said input frequency waves` to desired harmonic output frequency waves of substantially sine wave form comprising a phase shift transmission line connected adjacent one end thereof to said tuned output circuit of said amplifier means and comprising a plurality of iterative tandem-disposed phase shift sections each having a reactance value sutcient for contributing successive phase shifts in said input frequency waves therein in accordance with the order of said harmonic of said output frequency waves and each corresponding in phase shift to an integral fraction of one cycle of said input frequency waves, junction tap connection points for at least some of said successive phase shift sections for individually tapping off said successive phase shifted waves from said phase shift transmission line, terminating means for said phase shift transmission line adjacent the other end thereof comprising at least one of said phase shift sections disposed beyond the last one of said junction tap points, a plurality of rectifier means individually connected to said respective junction tap points for rectifying said successive phase shifted waves received from said phase shift transmission line, resistance means individually connected in series between at least some of said junction tap points and their said respective rectifier means for substantially equalizing the relative differences 7 in amplitude levels of said successive phase shifted waves therein, means including a common output circuit connected to and combining the outputs of Said rectified waves received from said respective rectifier means for obtaining in said output circuit said desired harmonic output frequency waves, said output circuit including therein a series resistance means connected with said plurality of rectifier means and having a sufficiently high impedance value with respect to the impedance `value of said phase shift transmission line to prevent said output circuit from shorting said phase shift transmission line and to equalize said desired harmonic frequency waves in said output circuit and minimize distortion of currents in said transmission line, said output circuit including therein a resonant circuit connected with said last-mentioned series resistance means and tuned substantially to said harmonic output frequency for filtering said desired harmonic frequency sine waves therein, and output circuit electronic amplifier means having the input thereof connected to said last-mentioned resonant circuit and having an output resonant circuit tuned substantially to said harmonic frequency for amplifying and further filtering said desired harmonic frequency sine waves therein.

3. Frequency multiplier apparatus in accordance with claim 2 wherein said phase shift transmission line cornprises a lumped constant type transmission line, and said reactance of each of said phase shift sections thereof comprises a combination of at least two of inductance, capacitance and resistance elements.

4. Frequency multiplier apparatus in accordance with claim 2 wherein said phase shift transmission line comprises an iterative phase shift network having at least References Cited in the file of this patent UNITED STATES PATENTS 1,514,735 Schriven Nov. 11, 1924 2,263,376 Blurnlein et al. Nov. 18, `1941 2,273,163 Wilson Feb. 17, 1942 2,401,405 Bedford June 4, 1946 2,414,541 Madsen Ian. 21, 1947 2,465,840 Blumlein Mar. 29, 1949 2,485,124 Westcott Oct. 1S, 1949 2,589,254 Hoeppner et al Mar. 18, 1952 

